Drive transmission



April'28, y1942. ,.1. w. F11- GERALD 2,281,277

DRIVE TRANSMISS ION Filed Deo. 50, 1940 Patented pr. 28, 1942 UNITEDSTATES ATENT OFFICE DRIVE TRANSBHSSION Application December 30, 1940,Serial No. 372,279

(Cl. I4- 214) 2 Claims.

This invention relates to improvements in drive transmissions suitablefor general use but especially adapted to engine starters.

In present day engine starters of the automatic type, which, because ofits low cost is used considerably more than the manual type, a pinion isautomatically axially propelled into mesh with the engine ring gear. Thepossibility of clashing or improper meshing of the gears and appreciablenoise is thus inevitable, and although recent developments have greatlyminimized these objections, they still exist.

With a view toward overcoming these objections it has been proposed fromtime to time to substitute` frictional driving members for vthe toothedpinion and gear, but heretofore all such proposals have involved aconstruction wherein at least one of the cooperating drive members had aconical surface to be brought into frictional driving engagement Withthe other member upon axial shifting of one or both of the members.

A wedge-like engagement was thus effected between the contactingsurfaces. This gave rise to a very serious objection, for at allportions of the conical surface except that lying on a theoreticalmedian transverse plane, slippage would have to occur between theengaging surfaces. Consequently a transmission built along those linescould not stand up in service. ual slippage would soon wear the surfacesto the point of uselessness.

It is, therefore, an object of this invention to provide a frictionaldrive transmission suitable for general use but especially well adaptedfor use in engine starters and similar installations, wherein thecontacting surfaces of the two drivmembers contact with a rolling actionentirely free from slippage.

More specifically, it is an object of this invention to provide a drivetransmission of the charactor described wherein the cooperating drivingmembers have a uniform diameter as distinguished from previoustransmissions of this type wherein the drive surface of at least one ofthe cooperating members was conical..

Another object of this invention is to provide a drive transmission ofthe character described wherein the establishment of a drivingconnection is effected without necessitating lateral or axial bodilyshifting of either of the two cooperating members. In this connection itis a further object of vthe present invention to provide a drivetransmission wherein the establishment of f The contina drivingconnection is effected by expanding one of the members radially.

Another object of this invention resides in the provision of anexpansible drive pulley composed partially of an elastic body having acircular outer surface and capable of axial compression to effect radialexpansion and consequent frictional driving engagement with acooperating pulley.

Another object of this invention resides in the provision of a novelmanner of transmitting dri ng force from a shaft to an elastic collarmounted on the shaft.

With the above and other objects in view, which will appear as thedescription proceeds, this invention resides in the novel construction,combination and arrangement of parts substantially as hereinafterdescribed, and more particularly dened by the appended claims, it beingunderstood that such changes in the precise embodiment of thehereindisclosed invention may be made as come within the scope of theclaims.

The accompanying drawing illustrates one complete example of thephysical embodiment of the invention, constructed in accordance with the`best mode so far devised for the practical application of theprinciples thereof, and in which:

Figure l is a view partly in side elevation and partly in section of adrive transmission constructed in accordance with this invention, saidview showing the drive in its inoperative condition;

Figure 2 is a view similar to Figure l but showing the parts in theiroperative positions with the drive pulley expanded into drivingengagement with the driven pulley; and

Figure is a detail sectional view through Figure l on the plane of theline 3 3.

Referring now particularly to the accompanying drawing, in which likenumerals indicate like parts, the numeral 5 designates a driven pulleywhich may be the flywheel of an internal combustion engine. The outersurface of this pulley is a regular surface of rotation and the axisabout which the pulley turns is fixed.

Adjacent to the cuter peripheral surface of the pulley 5 is a driveshaft G. This shaft is mounted in xed bearings (not shown) which hold itin an axially fixed position parallel to the axis ofthe pulley 5. If theinvention is applied to an engine starter for automobiles and the like,the drive shaft 6 may be the shaft of a starter motor 1.

Mounted on the shaft t is an expanding pulley designated generally bythe numeral 3. This pulley comprises a plurality of alternate metal andrubber washers or discs 9 and I0, respectively, assembled on the shaftbetween a fixed collar I I secured to the shaft and a movable collar I2slidable on the shaft.

The metal discs or washers are keyed to the shaft as at I3 but therubber discs or washers are not. Driving force is transmitted from theshaft to the rubber discs or washers through friction established andmaintained by placing the assembly in axial compression. The advantagesof a multiple plate clutch are thus obtained and slippage between the4drive shaft and the rubber or elastic discs or washers is prevented.

As will appear from Figure 1 the elastic discs or Washers ID' areslightly larger in diameter than the metal washers 9 so that theirperipheral edges jointly form the driving surface of the pulley.However, the effective diameter of the pulley is normally insufcient tocontact the pulley 5. In other words, the diameter of the elastic discsin the normal inoperative condition of the pulley is not great enough toengage the surface of the pulley 5; but inasmuch as the leffectivediameter of the pulley depends upon the state of compression of theassembly it may be expanded into driving engagement with the pulley 5when desired.

This is accomplished by placing the pulley assembly under axialcompression which expands the elastic discs or washers radially intofrictional driving engagement with the pulley 5 as shown in Figure 2.

Thus through control of the state of axial compression of the drivingpulley, complete control over the drive transmission may be maintained.Any suitable manner of placing the assembly in axial compression may beused, and for purposes of illustration the movable collar I2 is shown asbeing actuated by a medially pivoted lever I4 to which an actuator I5 isattached.

While in the description thus far, the pulley 5 is stated to be thedriven pulley and the pulley 8 the driver, it is of course apparent thatthe functions of these two pulleys may be reversed.

If the transmission is used as an engine starter, the motion of themechanism employed for compressing the pulley 8 to establish the drivingconnection may be used to close the switch controlling the motor I. Thespecific switch structure employed for this purpose forms no part ofthis invention, but to illustrate the combination the lever I 4 has beenillustrated as being grounded and engageable with a contact I6 tocomplete the motor circuit upon actuation of the lever in the directionnecessary to expand the pulley 8 as clearly shown in Figure 2.

From the foregoing description, taken in connection with theaccompanying drawing, it will be readily apparent that this inventionprovides an exceedingly simple but effective expanding pulley typetransmission which has all the advantages of a frictional drive withoutthe disadvantages inherent in previous constructions and resultingprimarily from slippage between the contacting surfaces. It is furtherapparent that this invention is admirably suited for use in automobileengine starters and when so used, all shock of starting will beeliminated.

What I claim as my invention is:

1. In a drive transmission: a pulley rotatable about a fixed axis andhaving an annular surface; a shaft rotatable on a xed axis parallel withthe axis of the pulley; means for selectively drivingly connecting anddisconnecting said pulley and the shaft, said means comprising ashoulder on the shaft; a plurality of alternate rubber and metal washersassembled on the shaft with one end of the assembly bearing against theshoulder, the rubber washers being loose with respect to the shaft andthe metal washers being keyed thereto, said washer assembly beingopposite the annular surface of the pulley, the metal washers having adiameter such as to leave substantial clearance between them and theannular surface of the pulley and the rubber washers vhaving a normalfree diameter at least as great as the metal washers but insufficient tocontact the annular surface of the pulley; and means for controlling thediameter of said rubber washers regardless of rotation of the shaft,said last named means including a part movable longitudinally of theshaft toward the shoulder thereon to place said assembly of washersunder axial compression and thereby expand the rubber washers radiallyinto driving engagement with the annular surface of the pulley, saidpart being movable away from said shoulder to relieve the rubber washersof axial compressive and peripheral torsional forces.

2. In a drive transmission: a member rotatable about a fixed axis andhaving a surface concentric to said axis; a shaft substantially parallelwith said axis and having a portion opposite said surface of rotation;spaced collars on the shaft; an expansible pulley mounted on the shaftbetween the collars for selectively drivingly connecting anddisconnecting said member and the shaft, said expansible pulleycomprising at least two washers of elastic material with a non-yieldingwasher interposed therebetween and keyed to the shaft, the diameter ofsaid washers being such that their periphery lies close to but is spacedfrom the surface of rotation of said rotatable member when the yieldablewashers are in their free state; and means for placing the expandingpulley assembly in compression between the collars to simultaneouslyexpand the elastic washers radially to a larger diameter than saidnon-yielding washers and into driving engagement with said surface ofrotation and to frictionally bind the elastic washers to the nonyieldingwasher, said means including a part exteriorly of the pulley assembly sothat the pulley assembly may be actuated between its operative andinoperative positions regardless of rotation of the shaft.

JOHN W. FITZ GERALD.

